1. Field of the Invention
The present invention generally relates to a method for forming a semiconductor device, and more particularly, the present invention relates to a method for forming titanium and titanium nitride for using as adhesion layer.
This application is a counterpart of Japanese application Serial Number 14439/2000, filed Jan. 24, 2000, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
In general, as high-integration advances, tungsten interconnection utilized tungsten has been a focus of constant attention because step coverage is fine.
FIG. 1A through FIG. 1D are cross-sectional views showing a method for forming a semiconductor device according to a conventional art. As shown in FIG. 1A, an insulating film 2 having a contact hole 3 is formed on a silicon substrate 1. A part of the silicon substrate 1 is exposed from the contact hole 3.
As shown in FIG. 1B, using CVD (Chemical Vapor Deposition) technique, a titanium film 4 is formed on the insulating film 2 and the exposed silicon substrate 1 surface. Here, the CVD technique is carried out introducing titanium tetrachloride and hydrogen gas. Then, the titanium film 4 is treated with nitrogen plasma ion. Therefore, the nitrogen plasma ion is generated using ammonia, and the titanium film 4 reacts with the nitrogen plasma ion. Then, a titanium nitride film 5 is formed on the plasma treated titanium film 4 using the CVD technique. Here, the CVD technique is carried out introducing titanium tetrachloride and ammonia gas.
As shown in FIG. 1C, for decreasing low resistance, the titanium nitride film 5 is annealed in the atmosphere of ammonia. Then, a tungsten film 6 is formed on the annealed titanium nitride film 5. Then, the tungsten film 6 is etched back. As a result, the tungsten film 6 is buried in the contact hole 3.
As described above, the plasma treating of ammonia is carried to increase adhesion between the titanium film 4 and a titanium nitride film.
However, since the plasma treating of ammonia has a high nitriding speed for titanium, the titanium film is completely converted the titanium nitride film. Besides, the silicon substrate 1 surface under the titanium film is also nitridized. Therefore, a silicon nitride is formed on the silicon substrate 1 surface. As a result, a contact resistance of the tungsten interconnection in a contact hole, is increased.
It is desired to decrease a contact resistance of the tungsten interconnection in a contact hole.
An object of the present invention is to provide a method for forming a semiconductor device that can decrease a contact resistance of the tungsten interconnection in a contact hole.
According to one aspect of the present invention, for achieving the above object, there is provided a method for forming a semiconductor device comprising: providing a semiconductor substrate; forming an insulating film having a opening; forming a titanium film so as to extend from the semiconductor substrate in the opening to the insulating film surface; plasma treating the titanium film with a mixed gas of hydrogen and nitrogen; and forming a titanium nitride on the titanium film.